The long-term goal of this research is to understand how environmental chemical signals impact the expression of drug metabolism enzymes (DMEs). DMEs of Phase I and II metabolism are actively involved in detoxification of xenobiotics and endogenous compounds and are a major source of drug inactivation and interference. Therefore, understanding the molecular events that begin with the ingestion of environmental compounds and drugs and result in DME upregulation is a key component of predicting drug-drug and drug environment interactions. Although it has long been recognized that DME gene expression is activated in the presence of their substrates, insights into the mechanisms of this induction have only recently been elucidated. In the past several years, the nuclear receptor (NR) PXR has been implicated as a key mediator of xenobiotic induction of DME gene expression in several vertebrate species. The recent completion of the C. elegans sequencing project revealed the existence of more than 260 nematode NRs including several that are closely related to PXR. Among these PXR-related NRs is NHR-8, which C. elegans requires for wild type resistance to xenobiotics. The role of NHR-8 in xenobiotic resistance suggests that like its vertebrate homolog, NHR-8 responds to the presence of xenobiotic toxic compounds by upregulating the expression of a detoxification network to remove the offending compounds. The research proposed here is designed to test this prediction by 1) describing the members of the nematode detoxification network within the C. elegans genome, 2) defining the DME loci that are upregulated by NHR-8, 3) discovering the regulation of NHR-8 expression, and 4) establishing a cell culture based NR signaling assay to investigate NHR-8 ligand binding. The C. elegans genomic sequence will be mined for DME-coding open reading frames. The resultant data will be characterized using a variety of phylogenetic and comparative genomic analyses to identify the relationships between the nematode and vertebrate proteins. The description of the C. elegans detoxification network will allow the production of a DME-specific DNA microarray that will facilitate the discovery of DMEs regulated by NHR-8. The modular nature of NR domains will be harnessed to produce transgenic animals bearing chimeric NRs containing defined DNA binding domains and NHR's ligand binding domain to probe NHR-8 for transcriptional activation in response to xenobiotics. [unreadable] [unreadable]